In recent years there has been a great amount of concern over the contribution of volatile organic compounds to environmental pollution. Use of chlorofluorocarbons propellants in aerosol spray compositions have been banned in the United States for more than a decade. Emissions of hydrocarbons such as the volatile hydrocarbons used as aerosol spray propellants, for e.g., n-propane or isobutane, have come under increasing scrutiny as potential sources of air pollution as well as organic solvents commonly used in aerosol spray compositions such as ethanol. Thus, there is a need for improved aerosol spray compositions such as hair spray packages which permit the consumer to effectively style the hair, but which possess reduced emission of volatile organic compounds.
Alternative means for producing aerosol composition packages with reduced environmental impact have been proposed that use compressed gases such as carbon dioxide or nitrogen instead of volatile hydrocarbon propellants as well as the use of pump-spray packages which employ no propellant whatsoever. Special valves and pumps have been developed for use with such packages. The valves employed in packages pressurized with compressed packages tend to be complex since the pressure over the life of the can must be carefully regulated so that the gas is not expended prior to the time that the last of the composition is discharged from the package. Pump spray containers are more difficult to match with the compositions to be sprayed since there is no propellant and the pump spray unit itself must create adequate atomization of the hair spray composition. To work effectively, a hair spray composition must have a specific volume mean particle size.
If the volume mean particle size of the hair spray composition is too small, then the consumer tends to use a lot of hair spray to style the hair. Much of the fine particles are lost to the atmosphere creating a pollution problem and waste of the product. If the volume mean particle size of the atomized hair spray composition is too large, the composition tends to wet the hair and render it sticky. The styling of the hair may even be lost in such a case. This also tends to be wasteful of product. In either case, the hair spray composition package tends to have a short use life.
Several means for controlling the volume mean particle size of atomized hair spray compositions are known. For self-pressurized aerosol compositions, the orifices present in a typical aerosol valve can be varied in size to obtain a finer or coarser spray. Addition of a vapor tap orifice will cause the atomized hair spray composition to become finer and will reduce the discharge rate. The orifice size on the actuator button attached to the aerosol spray valve can also be modified to change the ultimate particles of the volume mean particle size of the hair spray composition. For example, U.S. Pat. No. 3,137,416 to Shepherd et al. teaches a composition for an aerosol dispenser consisting of two immiscible liquid phases.
This patent teaches the variation of the size of the vapor tap orifice and an aerosol spray valve to provide spray patterns from coarse wet sprays to finely atomized dry sprays. Examples 33 and 34 teach hair spray packages which have reduced spray rates of 24 grams/minute (0.4 grams/second) versus an average of 70 grams/minute (1.17 grams/second) for conventional anhydrous product and points out that the lower spray rate is very advantageous as it provides a longer lasting product. The sprays are described as finely atomized, dry sprays which had good hair holding properties and drying times. Example 34 employs several hair fixative polymers and a plasticizer as well as 21.2% water and 49.4% ethanol along with 25% isobutane as a propellant. The water is employed so that the hair spray composition becomes a two phase composition which is said to reduce the flammability of the hair spray product.
U.S. Pat. No. 4,192,862 to Pengilly teaches a hair spray containing a hair spray resin and a drag reducing agent which is typically a high molecular weight polymer which is used in a very small amount (less than about 0.3% by weight of the hair spray composition) to improve the holding power of a hair spray composition. From the examples given, it appears that the high molecular weight polymer being used as a drag reducing agent has an effect on the mean average particle size of the atomized hair spray composition being discharged from a pressurized aerosol spray composition package. Pengilly teaches that the inclusion of the drag reducing agent polymer can reduce the amount of hair spray inhaled into the lungs which he refers to as the "respirable fraction" of the product.
Neither of the above patents appear to address themselves to reducing the volatile organic content emission of hair spray composition packages.